Relay and circuits therefor



Feb. 26 1924.

D. K. GANNETT RELAY AND CIRCUITS THEREFOR Filed Dec. 18. 1922 INVENTOR.a5 G ZZIZ/IMZZ ATTORNEY Patented Feb. 26, 1924.

UNITED STATES,

PATENT OFFICE.

nmron'rn x. GANNETT, or ELMHURST, NEW YORK, ASSIGNOR To AMERICAN TELE-rnozm am: TELEGRAPHCOMPANY, A coaroaa'rron or NEW YORK.

RELAY AND cmcurr's' mum-R;

Application filed December 18, 1922. Serial at. 607,873.

To all whom it may concern Be it known that I, DANFORTH K. GAN- NETT,residing at Elmhurst, in-the county of Queens and State. of New York,have invented certain Improvementsin Rela s and- Circuits Therefor, ofwhich the fol owing is a specification.

This invention relates to relays of the vibrating armature type, andmore particularly to arrangements for causing such relays to operatewith minimum bias effects.

\Vhile relays of this character are capable of a wide variety of uses,one. of the methods of employing the vibrating relay-of this inventionis for the purpose of generating telegraph reversals. Such reversalsconsist of a steady train of impulses or dots, the succeeding impulsesbeing usually of opposite signs, and currents of this character may beutilized for testing purposes in connection with telegraph apparatuses,repeater sets, etc.

operate with a minimum amount of bias, or,

in other words, that the reversals or sucmeans of these reversals, anyliability of error due to the bias of the testing current itself will beeliminated. Such bias is exemplified in a periodically reversing currentby either a longer resistance or a greater amplitude of the currentpulses of one polarity. It is, in general, the object of the inventionto provide arrangements for a vibrating relay whichwill cause the relayto be very stable with respect to bias so that imperfect adjustment ofthe relay or other variable factor will not introduce perceptible biasinto the generated reversals.

The invention may be more fully understood from the followingdescription when read in connection with the accompanying drawing inwhich Fig. 1 is a schematic circuit diagram of a the invention.

Figures 2 and 3 are graphic illustrations of the operation of the deviceofthe present invention under different conditions, Figi l illustrates aform of testing circuit to which the vibrating relay arrangement of theWhen used for such purposes, it is extremely desirable that thevibrating relay 7 the same direction.

preferred embodiment of.

present invention may be applied, Fig. 5 illustrates a modification ofthe arrangement shown in Fig. 1, in which thewinding for correctingbiasof the relay is'independent of the operating winding of'therelay andFig. 6 illustrates a still further. modification in which the correctingfunction of one rela is controlled by the. operation of another re ay. h

Referring to Fig. 1, a polar relay having windings 1 and 2 and anarmature 3 is illustrated, the armature 3 being adapted to vibratebetween fixed contacts 4zand 5, one

of which is connected to positive battery and the'other-of which isconnected to negative battery, the other terminals of these'batteriesbeing connected to ground. A suitable 'inductance. 6, which preferablyhas a high time constant, is connected in circuit with the winding 2,and a resistance 7 is included in circuit with the winding 1, thecircuits of both windings being arranged in parallel and connected toground at 8.

The windings 1 and '2 are so constructed that: acirculatingcurrentflowing through.

the windings in' series produces and additive effect, that is, bothwindings under these circumstances tend to shift the armature in Thecurrent flowing through the two windings in parallel to or from themid-point, however, willrproduce opposing effects upon the armature. Thecircuit arrangement is such that, when the armature is resting upon onecontact, the current flowing throughthe winding-2 and the inductance 6will be in such a direction as to tend to shiftthe armature to theopposite contact, while the current flowing through the winding land theresistance! will be in such a direction as tohold' the These cur-.

armature against the contact. rents will hereinafter be referred to asoperatingand holding currents respectively, and the windings 2 and 1will likewise be referred to as'oper'ating and holding windingsrespectively.

The operation is as follows:

Let us suppose that the armature 3 is resting against one of thecontacts, for example, the contact'4, and that a positive potential withrespect to ground is suddenly. applied.

to the contact4,.by*closingaswitch, for

example. A current is immediately established through the holdingwinding 1 and the resistance 7, tending to lock the armature against thecontact 4. It will be observed that the full battery potential isapplied to the terminals 3 and 8 of the circuit including the winding 1,so that the current flowing through the winding 1 will be independent ofthe resistance or inductance of the circuit including the winding 2.Consequently, the current which immediately flows through the holdingwinding 1 maintains a steady value so long as the armature 3 remainsagainst the contact 4:.

As soon as the battery potential is applied to the contact l, however, acurrent starts to build up in the circuit including the winding 2, but,due to the time constant of the inductance 6, it takes an appreciabletime for this current to build up. As soon as this operating currentreaches a value sufficient to overcome the effect or" the holdingcurrent flowing through the winding 1, the armature 3 leaves the contacta. The instant this occurs the holding current through the winding 1ceases, and a circulating current due to the discharge or the energystored in the magnetic field in the inductance 6 flows through saidinductance, through the resistance 7 and through the windings 1 and 2 inseries. This current flows through the winding 2 in the same directionas the current originally flowing from the contact 4, but it flowsthrough the winding 1 in a direction opposite to that of the holdingcurrent, so that the winding 1 now aids the winding 2 to sharply kickthe armature over against the negative contact 5. As soon as thearmature rests against the contact 5, the holding current flows throughthe winding 1 in the same direction as the circulating current, but in adirection opposite to that of the previous holding current, so that thewinding 1 tends to hold the armature against the contact 5. Thepotential now applied to the winding 2 is in a direction opposite tothat of the previous operating potential, so that the current built upin the inductance 6 begins to decay until it falls to zero and thenbegins to build up in the opposite direction. When the current builds upin the opposite direction through the winding 2 to a value sufiicient toovercome the holding current flowing through the winding 1, the armature3 leaves the contact 5 and a circulatng current flows through windings 1and 2 in series in such a direction that winding 1 assists the winding 2to sharply shift the armature to contact 4:.

If reference is now had to the graphic showin of Fig. 2 in which thedashed line L, represents the holding current and the dotted line Irepresents the operating current, it will be seen that it took a longertime for the current in the operating winding to build up in a directionto shift the armature from contact 5 to contact 4 than it did for theoperating current to build up to shift the armature originally fromcontact 1 to contact 5. This is for the reason that dur- 1g the firstseinicycle the operating current only had to build up from zero, whileduring the second semicycle a suflicient time must elapse for thecurrent to decay from the built-up value to zero and then build up to anoperating current in the opposite direction. At the end of the secondsemicycle when the operating current through the winding 2 has reached asullicient value to again shift the armature from contact 4 to contact5, the holding current through the winding 1 will hold the armature 3against the contact 5 as before. The operating current through thewinding 2, however, begins to decay until it becomes zero and builds upin the opposite direction to a value sutlicient to again shift thearmature. Since the current builds up to the same value during eachsemicycle (although in the opposite direction), the same length of timenow clapses between the shifting of the armature to the contact 5 andthe shifting of the armature back to the contact a as elapsed during thepreceding semicycle. A steady state has now been reached, and thearmautre will continue to automatically shift back and forth at equalintervals, as will be apparent from the curve of Fig. 2, in which theeffective current operating upon the armature (that is, a current equalto the algebraic sum of the operating and holding currents) is indicatedby the full line curve, this curve commencing in the diagram at thepoint where the steady state conditions begins. T is frequency ofvibration of the armature may be easily adjusted by means of theresistance 7 which controls the value of I The larger 1,, is made thelonger will be the time interval before I builds up to a valuesufficient to overcome T The curves in Fig. 2 were plotted from thecalculations made in accordance *ith formulae which will be givenhereinafter. In making these calculations, and hence in plotting thecurves, the time of travel of the relay arn'iature was neglected, theconstants of the relay windings were neglected, and it was assumed thatthe relay shifted its armature just wh n the opcratin g current reacheda value equal to that of the holding current, but in the oppositedirection. These assumptions involve only a very slight error, and hencethe curves of Fig. 3 substantially represent the operation of the relay.

It will be seen that a relay such as illustrated in Fig. 1 and operatingas indicated in Fig. 2 will be subject to bias to a very small extentonly, as the force tending to pull the armature away from the contact isroughly proportional to the length of time that the armature hasremained on said contact. In other words, the longer the armature restsupon a given'contact the greater becomes the value to which theoperating current builds up, and hence the greater becomes the forcetending to shift the armature from the position in which it is resting.In order to more fully understand the correctingaction against biaseffects, let us suppose that, instead ofpermitting the relay to operateautomatically as above de scribed, thearmature of the relay be forciblyoperated at the same speed as its free vibrations, but with a 20% bias,that is, with the armature resting upon the positive contact, a timeonly eight-tenths as long as indicated in the curve of Fig. 2 and on thenegative contact a time one and two-tenths as lon as indicated in Fig.2. The currents will then take the form indicated by the curvesof Fjig.

Referring to Fig. 3, it will be observed that when the positivepotential is applied to the armature of the relay the operating currentbegins to build upin the negative direction and continues to so build upfor eighttenths of a semicycle. As this period is much longer than thefirst semicycle shown in Fig 2, the operating current builds up to amuch greater value than that necessary to overcome the holding currentbefore the armature shifts. As soon as the armature shifts. theoperating current begins to decay and to build up in the oppositedirection, this 'operation continuing for one and two-thirds semicycles.Owing to the great value in the negative direction to which theoperating current has been built up, this time, while greater than thatof the previous reversal, does not permit the operating current to buildup in the positive direction to a value equal to the negative operatingcurrent when the next reversal takes place at the point marked 3. Thecurrent now begins to decay and build up in the opposite direction untilthe reversal at the point marked 4: takes place. The'operatingcurrentdoes not in this instance build up to as great a value as at the pointmarked 2. For each succeeding cycle, theoperating current builds up to agreater positive value but builds up to a smaller negative value until asteady condition is reached, as indicated at the point marked 9, atwhich point the operating current attains its greatest positive value.At the point designated 10, the operating cur rent has not beenpermitted to decay sufficiently to reach zero, before the armature isagain shifted. From this point on the operating current passes throughthe same riations for each succeeding cycle.

It will be observed that after the steady state condition is reached atthe point- 9 the axis of the operating current is shifted in a positivedirection a distance marked D This represents an effective directcurrent through the operating winding upon which direct current analternating current is su perposed. This direct current component is insuch a direction as to tend to counteract the bias. The holding current,on theother hand, has shifted in a negative direction to the extentindicated by the horizontal line marked axis of I This axisis drawn sothat the area included within the dashed line 'curve corresponding to anegative semicycle will be equal to the area circumscribed above saidline by the dashed lines of the positive semicycle. The shifting of theaxis of I represents the effective bias due to the prolongation of thenegative semicycle. and it will be apparent that the shifting of theaxis of I in the positive direction is much greater thanis necessary toovercome the negative shifting of the axis of I The resultant currentoperating upon the armature is indicated by the full line curve, and itsaxis has shiftedin a positive direction a distance marked D. Thisrepresents the effective restoring current which tends to oppose theforce that produces the bias. For the conditions and circumstancesassumed in the drawing, the effective restoring current is about equalto the maximum normal current through either winding. The restoringcurrent increases rapidly in amplitude with the magnitude of the forcestending to produce bias. This results in very stable operation of therelay. In practice, the constants of the circuit should preferably bechosen so that the relay core is not saturated by the operating flux.

The presence of the restoring force represented by D may be explainedphysically by noting that as the relay armature 3 vibrates, a.periodically reversing E. M. F. is

impressed across the circuit 3-2-6-8. If the operation of the relay isslightly biased, the armature 3 resting longer on one contact than onthe other, the Fourier series repre senting the E. M. F wave wouldpossess a small D. C. voltage component. The D. C. impedance of winding2- and inductance 6, however, is small compared with the A. C. impedanceat the frequency of vibration of the relay and therefore the currentwhich flows will possess a relatively large D. C. componentnotwithstanding that the D. C. voltage is small. This D. C. component isrepresented by D in Fig. 4: and as noted above is in such a direction asto strongly oppose the forces which tend to bias the operation of therelay.

As has already been stated, the curves of Figs. 2 and 3 were computedfrom formulae. The formuiae are derived as follows:

Given inductance L and resistance R in series with source of voltagewhich applies constants of inductance 6 in Fig. 1. Taking 25:0 when thevoltage changes from e to +6, the current is 6 where I I IS the currentin the cmcuit when :0, w equals and E is the in base oi the rlaperianlogarithms. T T

Let it as s is reversed when t t Let the alue of i when zf t tbe lc,I.20 Then The extreme values of current are k I and ia I. The location ofan axis half way between these values is given by very approxnn piyequal to the distance to the axis so .ced that the areas of the curveeach side of it are equal. In other words it very closely represents thevalue of the D. G. component of the current which flows.

when 6 :5 D 0. For this condition,

expression gives the amplitude of cat peaks in inductive circuit 3 l i econsisting of periodic unnased rever are is applied.

mple o'r the manner in which 3 i; ent of Fig. 1 may be attention iscalled to the telegraph 'cstng circuit illustrated in Fig. 4. Thereconprising the winnings 1 and 2 and 8 vibrating between contacts 4 ando tance 6 connected in series with the w :16 g 2 and resistances 7 and'11" in series with the windin 1. The ground connection 8 extending fromthe terminals of the resistance and inductance legs passes over anormally open contact of the jack J, so that when the plug P is insertedin the jack, the contact is closed, thereby completing the operatingcircuit. As the armature 3 is directed against one of the contacts, thefull battery potential to ground is applied to the windings of the relayand the relay commences to operate as already described. The armature 3has a connection 12 extending through a contact of a jack J and throughthe windings of polar relays PR PR PR etc, to ground, so that successivepositive and negative impulses pass over the contact 3 of the masterrelay and through the condenser and. resistance 1 1 and through thewindings of the relays PR PR PR etc. These relays transmit successiveunbiased pulses over the jacks such as J to suitable testing circuits.The condenser and resistance arrangement 14 are for the purpose ofcausing a large momentary current to flow through the windings of relaysPR PR PR etc, at each instant of transfer of armature 3 from contact 4to 5 or from contact 5 to 4, so that relays PR PR PR etc, will be verypositively operated and will not introduce any bias of their own. Thefrequency at which the master relay vibrates will de pend upon theresistance in series with the winding 1. This resistance may be variedby operating a key K which controls the circuit of relay 13 adapted toremove a short circuit from about the resistance 7, thereby increasingthe efiective resistance in series with the winding 1. \Vhen the key Kis operated and the short circuit is removed from about resistance 7 thefrequency of the master relay will be increased. A suitable milliammeter14 may be plugged into the jack J by means of the plug P in order tocheck up the action of the master relay by means of the reading of themilliammeter.

In the arrangement of Fig. 1, the relay winding 2 performs a doublefunction of acting as an operating winding and also as a correctingwinding. As an operating winding, its function is to shift the armaturefrom the contact upon which it is at the moment resting to the oppositecontact as soon as the operating current has built up to a value greaterthan the holding current through the winding 1. As a correcting winding,its function is to apply a force to the armature tending to overcome anybiasing forces acting upon the armature. These functions may, however,be separated and performed by different windings. The arrangement shownin Fig. 5 illustrates one method of separating the functions.

In Fig. 5, winding 1 is the holding winding and winding 2 is theoperating winding. A resistance 9 is connected in series with theoperating winding and a capacity 10 and I in the opposite direction.

small resistance 11 are connected in series with the holding winding.The operation of the circuit thus far described will be as follows.Assuming that the armature 3 rests against the positive contact 4 andthat the circuit is closed by a suitable switch for example, a positivecurrent of full normal value at once flows throughthe operating winding2 and the resistance 9. This current is independent of the conditions ofthe circuit through the winding 1, as the full battery potential isapplied across the terminals of the circuit 2-9-8. At the same instant,however, a holding current flows through the winding 1 and charges upthe capacity 10. The value of this current will be greatest at theinstant of closing the circuit and, as the capacity charges up, thecurrent through the winding 1 will decrease. The holding current, at theinstant of closing the circuit, is greaterthan the operating currentthrough the winding 2, but when it decreases to a value slightly lessthan the operating current through the winding 2, the operating windingacts to shift the armature to the opposite contact 5. An operatingcurrent now flows through the winding 2 in the opposite direction and aholding current also flows through the winding 1 The holding currentagain tends to hold the armature against the contact 5 until it becomesless in value than the operating current, whereupon the operatingWinding shifts the armature back to the contact 4 and this processcontinues indefinitely.

The circuit thus far described has no effect to overcome bias for thereason that the impedance of the circuit 2-98 is practically the samefor the alternating current components as it is for the directcurrentcomponent which results from bias. In order to overcome the efi'ect ofbias, a third winding 2' is provided, which is so connected as to beenergized over the contacts 4 or 5, as the case may be. This winding isso poled that when the armature is resting upon a given contact thecurrent flowing through the winding tends to shift the armature awayfrom the contact. An inductance 6 is included in circuit with thecorrecting winding 2. This inductance makes the impedance of the circuitof the winding 2 very high for the alternating current componentsresulting from the shifting of the armature between the contacts 4 and5. Its resistance to direct current, however, is quite' low. In thenormal operation of the relay, if there is no bias tending to hold thecontact against one armature longer than the other, there will be nodirect current component and consequently the effect of the winding 2 uon the operation of the circuit is inapprecia le. As soon as theoperation of the relay bethe direction of this component is such thatthe winding creates a constant pull upon the armature in a directionopposite to the bias ing effect.

his not even necessary that the correcting winding be energized over thearmature j of the vibrating relay, as illustrated in Fig. 5, but thiswinding may be energized over the armature of any other relay in asystem of relays controlled by the vibrating relay. For example, Fig. 6shows in simplified form how the circuit arrangement of Fig. 4 may bemodified to permit of controlling the correcting winding 2 from one ofthe polar relays PR PR or PR,. In the case illustrated, the relay PRwhich in the circuit of Fig. 4 supplies current reversals to a testingcircuit, for example, is utilized for controlling the winding 2. To thisend, the winding 2, instead of being connected to the armature 3 of themaster relay, is connected to the armature of the polar relay PR and thecontacts of said polar relay are connected to positive and negativesources of potential respectively. Consequently, if, for any reason, theoperation of the master relay becomes biased and its armature restslonger upon one contact than the other, the polar relay PR will sooperate that its armature rests longer upon the corresponding contactthan the other contact. As a result, a direct current component flowsthrough the winding 2' in such a direction as to oppose the biasingeffect upon the armature 3. The inductance 6 is provided in circuit withthe winding 2 as before so that the winding is practically unaffected byalternating current components owing to its high impedance thereto,while its resistance is quite low to direct current components.

It will be obvious that the general principles herein disclosed may beembodied in many other organizations widely difierent from thoseillustrated without departing from the spirit of the invention asdefined in the appended claims.

What is claimed is:

1. A vibrating relay system including a polar relay having an operatingwinding. a holding winding and an armature adapted to rest upon eitherof two contacts connected to opposite potentials, means whereby when thearmature rests upon either of the contacts a steady current flowsthrough the holding winding tending to hold the armature against thatcontact and means whereby a gradually increasing operating current isbuilt up through the operating winding to shift the armature against theopposite contact.

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